Snowmobile suspension

ABSTRACT

A suspension for a snowmobile having a driven endless belt thereunder for propulsion; a wheel-supported resilient framework within and riding on the lower part of the belt, carries the rear sprockets for the belt, and supports the front and rear ends of the snowmobile chassis; and adjustable means are provided at one end of the chassis for compressing the framework against the sprockets at the opposite end of the framework for increase in the resilient chassis support, and to maintain the belt tight on the sprockets.

United States Patent Padwick m1.

1541 SNOWMOBILE SUSPENSION [72] Inventors: Herbert W. Padwick, 93 CalderCrescent; Lawrence P. Fay, 628 Royal Street, both of Regina,Saskatchewan, Canada [22] Filed: Sept. 24,1970

[211 App]. No.: 75,440

52 us. c1 ..l80/5 R, ISO/9.58, 305/27 51 Int. Cl. ..B62m 27/02 [58]Field of Search ..180/5 R, 9.24, 9.58; 305/27,

[56] References Cited UNITED STATES PATENTS 1,542,149 6/1925 Landry-Ml;.."....305/27 7 3,404,745 10/1968 I Smieja l80/5 R v j 3,285,676 11/1966 Hetteenl. ..-..'..-.305/27 3,483,936 12/1969 Nilsson ..180/5 R3,480,096 1 1/1969 Hammitt.... ..180/9.24

OTl-[ERPUBLICA'IIONS Polaris "7 1, Fist on the Freedom Trail AdvertizingBrochure of Polaris Industries, July 30, l970, pgs. 10 and 11.

Primary Examiner-Richard J. Johnson Attorney-Kent & Ade

[57] ABSTRACT A suspension for a snowmobile having a driven endless beltthereunder for propulsion; a wheel-supported resilient framework withinand riding on the lower part of the belt, carries the rear sprockets forthe belt, and supports the front and rear ends of the snowmobilechassis; and adjustable means are provided at one end of the chassisfor-compressing the framework against the sprockets" at the opposite endof the framework for increase in the. resilient chassis support, andtomaintain the .belt tight on the sprockets. I

; 8 Claims, 9

SNOWMOBILE SUSPENSION The present invention relates to the constructionof motor vehicles, such as those for travel over snow and ice, andwherein the driving element is in the form of an endless track or belt,driven by an internal combustion engine on the vehicle.

These vehicles, generally known as snowmobiles, usually consist of anopen light chassis or frame to carry one or two riders, and are frontsupported by steerable skis while the rear portion is carried onflexible jackknife type of wheels which ride the above mentioned belt.In order that the endless belt be kept in alignment while driven, it isusually provided with two parallel rows of spaced track holes, one alongeach side thereof, which are engaged by driving sprockets at one end andidler sprockets at the'other end. In such a construction, andparticularly when saidjack-knife wheels are used, no arrangement isprovided to keep the belt tight on the sprockets, so that any resiliencybetween the chassis and the wheels will permit the belt to flatten andlengthen as the chassis comes down and then, as the chassis rises, thebelt will suddenly tighten on the sprockets. This results in whipping ofthe belt at high speeds and may permit escape of one or more sprocketsto later ruin the belt as it tightens.

The principal object of the present invention is: to provide asuspension for the chassis of a snowmobile which will keep the belttight on the sprockets at all times and prevent such damage, whileproviding resiliency between the chassis and the wheels so they canaccommodate uneven ground surface and insulate the chassis from suddenshocks.

With the above important and other minor objects in view, which willbecome more apparent as the disclosure progresses, the inventionprincipally consists in the design, arrangement and construction of thevarious parts which will be later explained, reference being had to theaccompanying drawings wherein:

FIG. 1 is a side view of the front of a snowmobile.

FIG. 2 is a vertical longitudinal sectional view along the machine shownin FIG. 1.

FIG. 3 is a vertical cross sectional view of the machine taken along thedot and dash line 3-3 of FIG. 2.

FIG. 4 is an enlarged perspective view of thesnowmobile suspension readyfor the installation shown in FIG. 2.

FIG. 5 is a perspective view of a portion of the endless belt.

FIG. 6 is a reduced plan of a modified wheel arrangement for the railframework.

FIGS. 7 and 8 show different spring constructions as modifications ofthe rail framework.

FIG. 9 shows a torsion construction as a further modification for theframework rails.

In the drawings like characters of reference indicate correspondingparts in the several figures.

A frame 10 is formed from sheet metal which is pressed into an invertedboxing 11 (FIG. 2) of narrow width and nearly the full length of themachine. The forward end of the frame is dished as at 12 into a shapesomewhat similar to the front of a boat, so it will ride the snowbankswhile reinforced by forwardly extending vertical webs 13 from the frontend of the boxing. The sides of this dished portion are wider than theboxing and each come down at an angle 14 (FIG. 1) to flat gutters 15which outwardly project from the bottom of the boxing and extend thefull length therealong. These gutters, at the angled sides 14, formguarded foot rests for the feet of the rider. A horizontal motor stand16 is provided on the front of the boxing, and a rear framing 17 thereonis adapted to receive a padded seat'(not shown) for the rider or ridersto sit on. Guiding skis 18 support the forward dished part 12 of theframe and are suitably steered (not shown) while a cross guard rail 19is carried by the rear end of the boxing l 1.

An engine, preferably internal combustion, is indicated at 20 and isbolted at 21 to the stand 16 and thru an endless chain 22 drives asprocket 23 on a shaft 24 which passes through the boxing 11 and issuitably bearinged (not shown) in the walls thereof. This shaft, withinthe boxing, is provided with a pair of spaced sprockets 25 which drivean endless ground belt 26 of slightly narrower width than the inside ofthe boxing. A portion of this belt is shown in perspective in FIGQS andit will be notedthat each side is provided with a line of sprocketreceiving track holes 27 and 28 which are adapted to receive the teethof said driving sprockets 25.

The suspension 29 for the above described frame 10 is shown installedtherein in FIG. 2, and as this suspension is the principal basis of thepresent invention it is shown per se in enlarged perspective in FIG. 4,and will now be described:

A pair of spaced tapered straps orspring rails 30 and 31 form aframework for the suspension and both are downwardly sprung for apurpose later explained. The relatively wide rear ends of these railsare each forked at 32 and all such forks are secured to a cross axle 33which connects the rails and carries a pair of sprockets 34 and 35, eachof which are free to rotate in one of the forked ends of the rails.These latter sprockets are spaced apart the correct distanceto ride inthe lined holes 27 and 28 of the endless belt 26. The ends of the crossaxle 33 extend past the forked ends 32 of the rails and areveachprovided with a bearing 36 having an upwardly projecting standard 37.These standards pass through slots (not shown) in the gutters 15 andeach support a suitable shock absorber 38 (spring or hydraulie), theupper end of which is pivotally carried by a stand bracket 39 on therear surface of the boxing 11, one on each side. Accordingly, the rearend of the frame 10 is supported by the sprockets 34 and 35.

The front ends of the rails 30 and 31 are bent upwardly at a slant, asshown at 40, and their extreme upper ends are secured at 41 to a crossshaft 42, the ends of which pass through slots 43in the walls of theboxing and are adjustably mounted on bolts and nuts 44 to angle bars orbrackets 45 carried on the outer sides of the boxing walls. When thenuts and bolts 44 are adjusted, they move the cross shaft 42 in theslots 43 and end-shift the rails 30 and 31 against the rear axle 33 totightenthe belt 26 on the sprockets 34 and 35, while at the same timevarying the resiliency of the rails 30 and 31.

The framework of spring rails 30 and 31 is supported on a plurality ofwheels 46 which are bearinged on the rails. In the present showing,these wheels are in pairs, each on opposite ends of a plurality of axles47 which are carried in spaced relation along the rails. It will benoted that thewheels are staggered by using long and short axles andhalf ride on the belt 26 at the outer side of the sprocket holes 28 and29 while the other half ride on the belt at the inner sides of theseholes, as shown in FIG. 3'. It will also be noted that the axles 47 areevenly spaced apart along the rails 30 and 31, the bearings thereforbeing welded to the rails. Due to the rails being downwardly sprung, aspreviously mentioned, a resilient downward pressure is maintained on thebelt by the wheels and permitit to accommodate the various undulationsof the ground surface over which it travels, while smoothly supportingthe frame from the rear axle 33 and at-thefront adjustments 44, whilethe belt itself is held tightly to the sprockets 34-35.

It might be mentioned at this time that the wheels could be individuallycarried on alternating stub shafts, mounted along each of the springrails 30 and 31, without using cross axles therefor, as the shaft 42 andthe rear axle 33 would maintain the spacing of the rails.

Further, many manufacturers of snowmobiles are now using a system ofjack-knife wheels for their suspension, so-called because the axles ofthe wheelsv spring apart in the units. Such a one is shown in CanadianPat. No. 714,454, July 27, 1965 to Marier. FIG. 7 of this patent hasbeen copied in the present FIG. 6 for a better understanding, and nowexplained. A main cross shaft 48 normally has each end mounted in thesides of the main frame of the snowmobile and a pair of shorter parallelaxles 49 and 50 are positioned on each side. The axles each carry a pairof spaced inwardly projecting arms 51 and 52 which terminate in bearings53 mounted on the shaft 48, while a pair of coil springs 54 encircle thebearings and are each sprung between a set of the arms 51 and 52 tocomplete the unit. Any number of these units may be mounted along theinterior of the main frame, depending on its length, and constitutes thecomplete suspension therefor, a rear sprocket axle 33 also beingprovided in fixed bearings (not shown) for the propelling belt, and asused in this construction. The springs 54 of these jack-knife units takethe shocks of the support wheels 55. These units have proved practical,except as mentioned at the start of this specification, re the releasingof the sprockets by the belt. In the present suspension construction 29,these jack-knife units can be used to advantage for further resiliency,when attached as follows:

The ends of the main cross shaft 54 of each unit are mounted on thespring rails 30 and 31, either above or below, so the axles 49 and 50float freely on either side, and as many as needed are positionedtherealong. This is shown in FIG. 6 and it will be noted that the railsare located between each outer pair of wheels 55 of the units. Whilethese wheels travel on either side of the spaced track holes 27 and 28due to the axles being offset, these axles couldbe of different lengthsas per the present disclosure and the wheels track in the manner shownin FIG. 4, if desired. Under either arrangement, added resilience wouldbe built-in the suspension while the tread belt 26 would still bemaintained tight on the drive and idling sprockets.

From the above it will be seen that this new suspension 29 is builtaround the adjusted downward resiliency of the rails 30 and 31 againstthe rear axle 33, and while these rails appear flat in FIG. 2 and 4,their normal tendency or reaction is to lift the front wheels and beltoff the ground through the axle 46 as these wheels are the firstaffected by the sprung rails. Actually, it is to be assumed that theweight of the frame 10 is maintaining the belt in ground contact throughthe wheels and therefore the rails are in the. flat position. Theadjustments 44 are used to maintain the wheels in such contact with thebelt when properly adjusted. When the frame is heavy, the rails areinclined to lift at the center so the adjustments are operated tofurther compress the rails against the rear axle 33 and bring thiscentral part down. Conversely, when the frame is light, the

5 front wheels are inclined to lift, so the resilient pressure isreleased sufficiently to lower them.

As the adjustments 44 act through the slanted por tions ofthe rails andat the portion above the axle, 46, a series of three modifications forhinged control at this point are shown in FIGS.7, 8 and 9. Asinglelifting spring 56 is shown in FIG. 8 to hold the separated andhinged part 40 elevated above the horjzontal rail 30 to give therequired tension. In FIG. 7, a pairof abutting angle plates 57 arecarried by the two parts 40 and 30, which are resiliently and hingedlybrought together by an over riding coil spring 58. The arrangement inFIG. 9 is a torque system of bars 59 and 60 from the cross shaft 42 tothe rails 30 and 31, the torque being applied by a wrench (not shown) atthe socket heads 61' and 62. It will'be understood that the sameadjustment 44 is used in all figures for downward spring pressure on therails 30 and 31.

It will now be appreciated that we have developed a very simpleframework 30-31 for resiliently holding the belt wheels 46 to theirwork, including those 55, while smoothly supporting the main frame 10 asthe belt 26 undulates over uneven ground. While we have shown evenlyspaced axles along the rail framework on which the belt wheels aremounted, it will be seen that the jack-knife unit system of .wheels canbe used instead and would'resiliently improve the suspension, as shownin FIG. 6, while the elevated angled ends 40 of the framework rails canbe materially strengthened at the axle 46' by the modifications shown inFIGS. 7, 8 and 9. Once the adjustments 44 are set for agiven weight ofthe frame 10, no further adjustments thereto are needed, unless theweight is changed or the adjustments themselves slip.

What we claim as our invention is:

1. In combination with a snowmobile frame having an endless beltthereunder which is end sprocket driven for propulsion of the framethereon; a suspension for said frame, comprising: a wheel-supportedresilient framework within said belt and riding the ground-supportedface thereof; said framework resiliently supporting the front and rearend of said frame and carrying idler sprockets for the opposite endrotation of said belt; adjustments on said frame for end-moving theframework and said idler sprockets for frame-supporting resiliency ofthe framework, and to maintain the belt tight on said sprockets, and twowheel-supported resilient rails forming the framework and underlyingsaid frame; one of the ends of said rails being bent upwardly to connectwith a cross shaft, the outer ends of which pass through slots in theframe walls to connect with said adjustments on the exterior of theframe, said adjustments operating to move the ends of said cross shaftalong said slots, in the tightening and loosening of said belt.

2. A snowmobile frame suspension as defined in claim 1, wherein a crossaxle is mounted on the rear end of the framework to rotatably supportsaid idler sprockets, and the outer ends of said axle resilientlysupport the rear part of said frame, through shock ab sorbers.

3. A snowmobile suspension as defined in claim 1, wherein the front endsof said rails are separately hinged to the rear parts thereof andresiliently reinforced against hinging.

4. In combination with a snowmobile frame; a suspension therefor,comprising: a resilient wheel-supported framework; sprockets rotatablymounted across one end of said framework, and said end resilientlysupporting one end of said snowmobile frame, while the opposite end ofthe framework supports the opposite end of said frame; the central partof the framework downwardly sprung for resiliency between the frame andsaid framework supporting wheels; an endless belt encircling saidsuspension, with one end looped over and meshing with said sprockets,another end thereof looped over and meshing with further sprocketsrotatably carried by the frame, and said supporting wheels riding thelower interior of the belt; means carried by the frame for power drivingsaid latter sprockets; adjustment means at one end of the frame supportfor varying the resiliency of the framework to tighten or loosen thebelt on said sprockets, two wheelsupported resilient rails forming theframework and undcrlying said frame; one of the ends of said rails beingbent upwardly to connect with a cross shaft, the outer ends of whichpass through slots in the frame walls to connect with said adjustmentson the exterior of the frame, said adjustments operating to move theends of said cross shaft along said slots, in the tightening andloosening of said belt.

5. A snowmobile frame suspension as defined in claim 4, wherein a crossaxle is mounted on the rear end of the framework to rotatably supportsaid idler sprockets, and the outer ends of saidaxle resiliently supportthe rear part of said frame, through shock absorbers.

6. A snowmobile suspension as defined'in claim 4, wherein the front endsof said rails are separately hinged to the rear parts thereof andresiliently reinforced against hinging.

7. In combination with .a snowmobile frame having an endless beltthereunder and which is front sprocketdriven for propulsion of saidframe; a suspension therefor, comprising: a pair of spaced tapered andresilient rails supported on off-set wheels therealong to provide aportable framework below said frame; the rear wide ends of said railseach forked and carrying a cross axle therebetween, and the front narrowends of the rails turned upwardly at an angle andsecured to a 7 crossshaft; said cross axle rotatably mounting a pair of sprockets each ofwhich rotate in one of said forks; the outer ends of the cross axle eachconnected with a shock absorber on the snowmobile frame for rear supportthereof; the ends of said cross shaft passing through slots in the framesides and secured to brackets for front support of the snowmobile framefrom the framework; a drive shaft rotatably mounted across the frontpart of the snowmobile frame and carrying a pair of spaced sprocketstherealong; sprocket-receiving tracks along each side of said belt; saidbelt encircling the suspension with the tracks thereof meshing with thesprockets of the drive shaft and of the cross axle, and with the offsetwheels riding the lower interior face thereof on either side of thetracks; means on said brackets for adjustably shifting the ends of thecross shaft along said slots for increasing the frame support

1. In combination with a snowmobile frame having an endless beltthereunder which is end sprocket driven for propulsion of the framethereon; a suspension for said frame, comprising: a wheelsupportedresilient framework within said belt and riding the ground-supportedface thereof; said framework resiliently supporting the front and rearend of said frame and carrying idler sprockets for the opposite endrotation of said belt; adjustments on said frame for end-moving theframework and said idler sprockets for frame-supporting resiliency ofthe framework, and to maintain the belt tight on said sprockets, and twowheelsupported resilient rails forming the framework and underlying saidframe; one of the ends of said rails being bent upwardly to connect witha cross shaft, the outer ends of which pass through slots in the framewalls to connect with said adjustments on the exterior of the frame,said adjustments operating to move the ends of said cross shaft alongsaid slots, in the tightening and loosening of said belt.
 2. Asnowmobile frame suspension as defined in claim 1, wherein a cross axleis mounted on the rear end of the framework to rotatably support saididler sprockets, and the outer ends of said axle resiliently support therear part of said frame, through shock absorbers.
 3. A snowmobilesuspension as defined in claim 1, wherein the front ends of said railsare separately hinged to the rear parts thereof and resilientlyreinforced against hinging.
 4. In combination with a snowmobile frame; asuspension therefor, comprising: a resilient wheel-supported framework;sprockets rotatably mounted across one end of said framework, and saidend resiliently supporting one end of said snowmobile frame, while theopposite end of the framework supports the opposite end of said frame;the central part of the framework downwardly sprung for resiliencybetween the frame and said framework supporting wheels; an endless beltencircling said suspension, with one end looped over and meshing withsaid sprockets, another end thereof looped over and meshing with furthersprockets rotatably carried bY the frame, and said supporting wheelsriding the lower interior of the belt; means carried by the frame forpower driving said latter sprockets; adjustment means at one end of theframe support for varying the resiliency of the framework to tighten orloosen the belt on said sprockets, two wheel-supported resilient railsforming the framework and underlying said frame; one of the ends of saidrails being bent upwardly to connect with a cross shaft, the outer endsof which pass through slots in the frame walls to connect with saidadjustments on the exterior of the frame, said adjustments operating tomove the ends of said cross shaft along said slots, in the tighteningand loosening of said belt.
 5. A snowmobile frame suspension as definedin claim 4, wherein a cross axle is mounted on the rear end of theframework to rotatably support said idler sprockets, and the outer endsof said axle resiliently support the rear part of said frame, throughshock absorbers.
 6. A snowmobile suspension as defined in claim 4,wherein the front ends of said rails are separately hinged to the rearparts thereof and resiliently reinforced against hinging.
 7. Incombination with a snowmobile frame having an endless belt thereunderand which is front sprocket-driven for propulsion of said frame; asuspension therefor, comprising: a pair of spaced tapered and resilientrails supported on off-set wheels therealong to provide a portableframework below said frame; the rear wide ends of said rails each forkedand carrying a cross axle therebetween, and the front narrow ends of therails turned upwardly at an angle and secured to a cross shaft; saidcross axle rotatably mounting a pair of sprockets each of which rotatein one of said forks; the outer ends of the cross axle each connectedwith a shock absorber on the snowmobile frame for rear support thereof;the ends of said cross shaft passing through slots in the frame sidesand secured to brackets for front support of the snowmobile frame fromthe framework; a drive shaft rotatably mounted across the front part ofthe snowmobile frame and carrying a pair of spaced sprockets therealong;sprocket-receiving tracks along each side of said belt; said beltencircling the suspension with the tracks thereof meshing with thesprockets of the drive shaft and of the cross axle, and with the offsetwheels riding the lower interior face thereof on either side of thetracks; means on said brackets for adjustably shifting the ends of thecross shaft along said slots for increasing the frame support resiliencyof the framework, and tightening the belt on said sprockets; and meansfor driving said drive shaft.
 8. A snowmobile suspension as defined inclaim 7, wherein the front ends of said rails are separately hinged tothe rear parts thereof and resiliently reinforced against hinging.